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https://github.com/Dasharo/systemd.git
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ab14aa23ae
Currently `systemd-sysctl` binary is used in `systemd-sysctl.service` which is mostly configured as `oneshot`. There are situations where one would like to use systemd to maintain Sysctl configurations on a host, using a configuration managers such as Chef or Puppet, by apply configurations every X duration. The problem with using `systemd-sysctl` is that it writes all the Sysctl settings, even if the values for those settings have not changed. From experience, we have observed that some Sysctl settings cause actions in the kernel upon writing(like dropping caches) which in turn cause undesired side effects. This patch tries to minimize such side effects by comparing values before writing.
138 lines
3.6 KiB
C
138 lines
3.6 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "af-list.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "log.h"
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#include "macro.h"
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#include "path-util.h"
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#include "socket-util.h"
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#include "string-util.h"
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#include "sysctl-util.h"
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char *sysctl_normalize(char *s) {
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char *n;
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n = strpbrk(s, "/.");
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/* If the first separator is a slash, the path is
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* assumed to be normalized and slashes remain slashes
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* and dots remains dots. */
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if (n && *n == '.')
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/* Dots become slashes and slashes become dots. Fun. */
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do {
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if (*n == '.')
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*n = '/';
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else
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*n = '.';
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n = strpbrk(n + 1, "/.");
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} while (n);
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path_simplify(s);
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/* Kill the leading slash, but keep the first character of the string in the same place. */
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if (s[0] == '/' && s[1] != 0)
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memmove(s, s+1, strlen(s));
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return s;
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}
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int sysctl_write(const char *property, const char *value) {
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char *p;
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assert(property);
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assert(value);
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p = strjoina("/proc/sys/", property);
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path_simplify(p);
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if (!path_is_normalized(p))
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return -EINVAL;
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log_debug("Setting '%s' to '%s'", p, value);
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return write_string_file(p, value, WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_SUPPRESS_REDUNDANT_VIRTUAL);
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}
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int sysctl_writef(const char *property, const char *format, ...) {
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_cleanup_free_ char *v = NULL;
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va_list ap;
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int r;
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va_start(ap, format);
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r = vasprintf(&v, format, ap);
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va_end(ap);
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if (r < 0)
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return -ENOMEM;
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return sysctl_write(property, v);
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}
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int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value) {
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const char *p;
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assert(property);
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assert(value);
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if (!IN_SET(af, AF_INET, AF_INET6))
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return -EAFNOSUPPORT;
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if (ifname) {
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if (!ifname_valid_full(ifname, IFNAME_VALID_SPECIAL))
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return -EINVAL;
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p = strjoina("net/", af_to_ipv4_ipv6(af), "/conf/", ifname, "/", property);
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} else
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p = strjoina("net/", af_to_ipv4_ipv6(af), "/", property);
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return sysctl_write(p, value);
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}
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int sysctl_read(const char *property, char **ret) {
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char *p;
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int r;
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assert(property);
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p = strjoina("/proc/sys/", property);
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path_simplify(p);
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if (!path_is_normalized(p)) /* Filter out attempts to write to /proc/sys/../../…, just in case */
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return -EINVAL;
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r = read_full_virtual_file(p, ret, NULL);
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if (r < 0)
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return r;
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if (ret)
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delete_trailing_chars(*ret, NEWLINE);
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return r;
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}
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int sysctl_read_ip_property(int af, const char *ifname, const char *property, char **ret) {
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const char *p;
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assert(property);
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if (!IN_SET(af, AF_INET, AF_INET6))
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return -EAFNOSUPPORT;
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if (ifname) {
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if (!ifname_valid_full(ifname, IFNAME_VALID_SPECIAL))
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return -EINVAL;
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p = strjoina("net/", af_to_ipv4_ipv6(af), "/conf/", ifname, "/", property);
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} else
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p = strjoina("net/", af_to_ipv4_ipv6(af), "/", property);
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return sysctl_read(p, ret);
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}
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